DE 195 20 916 A1 and DE 102 56 584 of the applicant and DE 2008 013 109 A2 already disclose devices in which the liquid is passed without stagnation to the dialysis devices.
DE 2008 013 109 A1 and DE 195 20 916 A1 show two main lines and loop-forming secondary lines branched off therefrom. Apart from the higher installations costs and the confusing hose routing a large amount of liquid must circulate so that enough liquid flows through all branches. As a consequence, the reverse osmosis or the circulating pump has to be designed with a much greater size to ensure overflow also during return.
As a consequence, one must expect an increased heating of the permeate and a microbial contamination risk resulting therefrom for osmosis and ring line.
Moreover, further drawbacks of this arrangement are the great flushing volume which is e.g. needed after a chemical disinfection so that toxic residues are avoided, as well as the temperature losses during hot cleaning that are caused by the larger surface of the distribution system.
Another serious drawback of all of these devices is that a coupling to a dialysis device without dead space or with low dead space is not possible.
Although the liquid circulates in the main and loop-forming branch lines, the liquid stagnates in the feed line within the dialysis device. Hence, colonization by germs may occur and there is the risk of recontamination of the main and loop-forming branch lines.
A further drawback is the handling of the branch or secondary ring line consisting of two hoses. It is only with great efforts that the high hygiene demand of a dialysis station can be satisfied with respect to the surface hygiene of the hoses which are partly also lying on the floor.
An essential drawback is the handling and the risk of burning at the arising high surface temperatures during hot cleaning, as well as the considerable heat loss in the environment.
In addition the connection to the dialysis device is not without dead spaces, so that even in the case of a circulating liquid within the loop-forming branch lines the coupling piece is not back-flushed. There is thus an increased risk of the colonization by germs and the propagation of germs, particularly in the coupling valve area, and of ensuing germ re-transportation into the main line.
Moreover, direct sampling for controlling the microbiological purity or the chemical composition of the liquid at the transfer point to the dialysis device has so far not been possible.
Moreover, the used coupling materials are of special steel, they are difficult to work on, they are expensive and have to be protected during hot cleaning against contact and heat loss.